Speckle artifacts as viewed in images projected on a display surface by a projector can be reduced. At least one spatial light modulator, illuminated by one or more light sources, can be imaged to a screen by a projection lens. A deflector subsystem can be provided in image space, proximate to the lens, where the image light emerges. In this location, image light directed to any given field point on the display surface is convergent, but can appear collimated. The deflector subsystem can include a tilted optical plate that is rotated in a plane along an axis. As the deflector subsystem is temporally rotated, the image light to any given field point traverses different optical paths, varying the angular diversity to reduce perceivable speckle by changing at least the angle of incidence to the screen.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A system for reducing speckle artifacts, comprising: a light source configured to emit light that is at least partially coherent; a projection lens configured to output the light as a convergent light beam towards a location on a target surface; a despeckling device with an optical axis and that is positionable between the projection lens and the target surface in a light path of the light, the despeckling device having at least one optical plate comprising an inner surface and an outer surface that are tilted with respect to the optical axis and that are configured to allow light emerging from the projection lens to enter the at least one optical plate through the inner surface and to exit the at least one optical plate through the outer surface, the at least one optical plate is rotatable about the optical axis to temporally and angularly deflect the convergent light beam through a plurality of angular orientations toward the location on the target surface; and a spatial light modulator positionable between the light source and the at least one optical plate, the spatial light modulator being configured to produce imaged light with at least one image pixel by modulating the light that is at least partially coherent.
2. The system of claim 1 , wherein the inner surface or the outer surface is tilted with respect to a line perpendicular to the optical axis by a tilt angle, wherein the outer surface is nonparallel to the inner surface at a wedge angle with respect to the inner surface such that the outer surface of the at least one optical plate is tilted further away from a line perpendicular to the optical axis than the tilt angle.
3. The system of claim 2 , wherein the at least one optical plate is configured to wobble in rotating in the despeckling device.
4. The system of claim 2 , wherein the at least one optical plate is configured to angularly deflect the convergent light beam by an amount that is based on: a refractive index of the at least one optical plate; a thickness of the at least one optical plate; the tilt angle; and the wedge angle.
5. The system of claim 4 , wherein the thickness of the at least one optical plate and the tilt angle are configured to limit an amount of astigmatism and coma to within 1/20 of a wavelength.
6. The system of claim 2 , wherein the at least one optical plate includes a first optical plate and a second optical plate that are rotatable with respect to each other to change the wedge angle.
7. The system of claim 2 , wherein the at least one optical plate is rotatable at a rate that is in a range of 200 revolutions per minute to 3600 revolutions per minute.
8. The system of claim 2 , wherein the at least one optical plate is a meniscus-type lens.
9. The system of claim 2 , wherein at least one of the inner surface or the outer surface is curved.
10. The system of claim 9 , wherein a radius of curvature for the inner surface or the outer surface is in a range of 5 meters to 50 meters.
11. The system of claim 1 , wherein: the target surface is a screen, the system is in a projector system for a theatre, the despeckling device is configured to limit a maximum spatial displacement of the at least one image pixel to a given area on the screen to less than or equal to half of a projected pixel width.
12. The system of claim 11 , wherein at least one of the inner surface or the outer surface is curved by an amount that is based on a distance between the projector system and the screen in the theatre.
13. The system of claim 1 , wherein the despeckling device further comprises: a housing that retains the at least one optical plate at a tilt angle with respect to the optical axis of the despeckling device; and an actuator configured for rotating the at least one optical plate at a rotational velocity, wherein the at least one optical plate has a refractive index and an optical thickness.
14. A despeckling device for reducing speckle artifacts, the device comprising: at least one optical plate having an inner surface and an outer surface through which to transmit light, the inner surface and the outer surface being tilted with respect to an optical axis of the despeckling device that is positionable between a projection lens and a target surface in a light path of light from the projection lens to the target surface, the inner surface and the outer surface are configured to allow the light emerging from the projection lens to enter the at least one optical plate through the inner surface and to exit the at least one optical plate through the outer surface; a housing for holding the at least one optical plate at a tilt angle to a mechanical axis of the despeckling device such that the inner surface and the outer surface of the at least one optical plate are tilted with respect to the mechanical axis; and an actuator configured for rotating the at least one optical plate at a rotational velocity about the optical axis to deflect, angularly and temporally, a convergent light beam of light through a plurality of angular orientations toward a location on the target surface, wherein the at least one optical plate is positionable closer in a light path to the target surface than a spatial light modulator that is configured to be positioned between the at least one optical plate and a light source and that is configured to produce imaged light with at least one pixel by modulating the light that is at least partially coherent.
15. The despeckling device of claim 14 , wherein the actuator is a motor that is configured to rotate the at least one optical plate.
16. The despeckling device of claim 14 , wherein the device is configured for directing a plurality of light beams toward an associated location on the target surface.
17. The despeckling device of claim 14 , wherein the at least one optical plate has a refractive index and an optical thickness, wherein the at least one optical plate is configured to deflect the beam of light toward the location based on the refractive index, the optical thickness, a wedge angle between the inner surface and the outer surface, and the tilt angle.
18. The despeckling device of claim 14 , wherein the at least one optical plate is interchangeable with a second optical plate from a suite of optical plates that include a single-wedged plate, a dual-wedged plate, a single curvature wedged plate, and a meniscus plate.
19. A method comprising: directing, by a projection lens, at least partially coherent light, emitted by a light source, as a convergent light beam towards a location on a target surface; modulating, by a spatial light modulator positioned between the light source and an optical plate of a despeckling device, the at least partially coherent light to produce imaged light with at least one image pixel; allowing light emerging from the projection lens to enter the optical plate of the despeckling device through an inner surface of the optical plate and to exit the optical plate through an outer surface of the optical plate, the inner surface and the outer surface being tilted with respect to an optical axis of the despeckling device, the despeckling device being positioned between the projection lens and the target surface in a light path of the light; and rotating the optical plate about the optical axis to deflect the convergent light beam temporally and rotationally through a plurality of angular orientations toward the location on the target surface.
20. The method of claim 19 , further comprising deflecting the convergent light beam by an amount that is based on the inner surface of the optical plate and the outer surface of the optical plate that is nonparallel to the inner surface.
21. The method of claim 20 , wherein the amount is further based on a wedge angle between the inner surface and the outer surface of the optical plate.
22. The method of claim 19 , wherein the optical plate wobbles in rotating about the optical axis.
23. The method of claim 19 , further comprising deflecting the convergent light beam by an amount that is based on: a refractive index of the optical plate; a thickness of the optical plate; and a surface configuration of the inner surface or the outer surface of the optical plate.
24. The method of claim 19 , wherein the target surface is a target surface profile of least dither of the convergent light beam at any given position on the target surface, the method further comprising: positioning the target surface profile of least dither to match a surface profile of a display, wherein a maximum dither at the display is a projected image pixel width.
25. The method of claim 23 , wherein the amount is based on the surface configuration of the inner surface and the outer surface of the optical plate, the inner surface being flat and the outer surface being nonparallel to the inner surface.
26. The method of claim 19 , wherein modulating, by the spatial light modulator, the at least partially coherent light comprises modulating the at least partially coherent light towards the location on the target surface to produce an image pixel.
27. The method of claim 26 , further comprising deflecting the image pixel at the location on the target surface with a spatial displacement having a maximum limit that is based on: a wedge angle of the outer surface with respect to the inner surface; a tilt angle of the optical plate with respect to an axis of rotation of the optical plate; a curvature of the outer surface or the inner surface; and an amount of wobble of the optical plate in rotating about the optical axis.
28. The method in claim 27 , wherein the maximum limit of the spatial displacement for the image pixel is less than or equal to half of a projected pixel width.
29. The method of claim 19 , further comprising: operating the despeckling device with an image projection system in a theatre.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
February 18, 2016
February 16, 2021
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